Level control assemblage for vehicles

ABSTRACT

A level control assemblage for vehicles for stabilizing the distance between the vehicle body and one or more wheelsupporting means independently of load variations at the vehicle and maintaining the distance constant at a preselectable value in which setting or regulating cylinders are connected in series with spring components between the vehicle body and the wheelsupporting means. The pressure spaces of the setting cylinders are connected, dependent upon the distance between the vehicle body and the wheel-supporting means, via one or more level control valves to which the distances are, via linkages communicated, either with a pressure source or with a tank conduit, with the length of the linkages being continuously variable by means of piston-cylinder units installed in the linkages.

United States Patent [72] Reiner Hovorka Wuppertal-Barmen, Germany [211App]. No. 817,045 [22] Filed Apr. 17, 1969 [45] Patented Nov. 16, 1971[73] Assignee Langen & Company Dusseldorf, Germany [32] Priority May 15,1968 [33] Germany [31] P17 55 480.2

[54] LEVEL CONTROL ASSEMBLAGE FOR VEHICLES 5 Claims, 4 Drawing Figs.

[52] US. Cl

[51] Int. Cl 860g 17/04 [50] Field of Search 280/6, 124 F, 6.1, 6.11,DIG. 1; 267/65 56] References Cited UNITED STATES PATENTS 2,978,2544/1961 Bundorf 3,071,394 1/1963 Miller lnventor 3,074,739 1/1963 Alfieri280/124 3,209,784 10/1965 Schwartz 280/DIG. 1

FOREIGN PATENTS 1,124,833 3/1962 Germany 280/124 PrimaryExaminer-Kenneth H. Betts Attorney-Holman & Stern ABSTRACT: A levelcontrol assemblage for vehicles for stabilizing the distance between thevehicle body and one or more wheel-supporting means independently ofload variations at the vehicle and maintaining the distance constant ata preselectable value in which setting or regulating cylinders areconnected in series with spring components between the vehicle body andthe wheel-supporting means. The pressure spaces of the setting cylindersare connected, dependent upon the distance between the vehicle body andthe wheel-supporting means, via one or more level control valves towhich the distances are, via linkages communicated, either with apressure source or with a tank conduit, with the length of the linkagesbeing continuously variable by means of pistoncylinder units installedin the linkages.

LEVEL CONTROL ASSEMBLAGE FOlR VEHICLES BACKGROUND OF THE INVENTION It isknown in the art, and attention is invited to German Provisional Pat.No. 1,124,833 to provide such a level control.

device. The prior device employs a single-acting cylinder provided witha return spring which can be loaded with gas or a liquid by means of arotary slide valve and thus increase the length of linkage. On the otherhand, it is possible to lessen the length of the linkage by discharginggas or liquid.

The disadvantage of this particular arrangement resides in the fact thata sensitive setting of a certain level position is possible only by apulse-type actuation of the rotary slide valve. In addition, a rotaryslide valve is not so tight from the structural viewpoint that repeatedcorrection of the height of the vehicle is not required.

According to another proposal disclosed in the above-mentionedProvisional Patent, a double-acting cylinder equipped with a singlepiston rod is displaced via a transmitter cylinder having equaleffective faces. However, such an arrangement is operable only with airsince a blocking occurs with a substantially incompressible liquid dueto the known differential effect unless storage components areinstalled. It should be pointed out that even with a hydrostatic linkageoperating satisfactorily under traction and compression, certaindisadvantages occur and in particular it is difficult to compensate forvolume variations caused by leakages or variations in temperature.

SUMMARY OF THE INVENTION It is an object of the present invention toprovide a level control assemblage for vehicles which overcomes theabove and other disadvantageous features existing in the art and toprovide a sensitive, continuous, and maintenance-free length variationof the linkage with the leakage oil and variations in temperature beingcompensated for automatically and the setting can be effected from anydesired location particularly from the drivers compartment.

The present invention solves the problem by providing a piston-cylinderunit which is a single-acting cylinder having a single piston rod andreturn spring, with the piston being loaded hydraulically counter to theforce of the return spring and the pressure in the liquid beingmaintained substantially constant by means of an adjustable pressurecontrol valve provided with an outflow aperture.

In a particularly efficacious embodiment of the invention, thepiston-cylinder units of each vehicle side may be loaded jointly and itis also possible to adjust the height of the front and rear sections ofthe vehicle separately and for trimming the vehicle in the unloadedstate, the initial tension of the return spring and the basic length ofthe linkage should be variable.

By the utilization of a pressure control valve having an outflowopening, leakage losses as well as volume increases due to temperaturerise are compensated for automatically. In as much as thepiston-cylinder units operate substantially statically, there is only aminimum consumption of fluid which is covered from the pressure sourcealready present for supplying the setting or regulating cylinderswithout an impairment of other functions.

Further objects and advantages of the invention will become more readilyapparent to those skilled in the art from the following detaileddescription and annexed drawings in which drawings:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic viewillustrating the essential components ofthe invention,

FIG. 2 is a view generally similar to FIG. 1 illustrating the manner inwhich the piston-cylinders of one vehicle side are loaded jointly,

FIG. 3 is a view along the lines of FIG. 1 illustrating the meanswhereby the heights of the front and rear sections of the vehicle can beset separately, and

FIG. 4 is a fragmentary view, partly in elevation and partly in crosssection depicting means whereby the basic length of the linkage means isvariable mechanically and means for adjusting the initial tension of thereturn spring means of each piston-cylinder unit installed in thelinkage means.

DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 1, it will benoted that a vehicle (not illustrated in detail) is provided with a rearaxle 1 on which are suitably supported rear wheels 2 and 3. Front wheels4 and 5 are operably associated with wheel steering and suspensionarrangements 6 and 7.

It will be noted that the rear axle 1 braces itself against the vehiclebody (not shown), by means of setting or regulating cylinders 8 and 9respectively and the steering and suspension arrangements 6 and 7 bracethemselves against the vehicle body via setting or regulating cylinders14 or 15.

The cylinders 8 and 9 are provided with pressure spaces 10 and 11 whichare in communication with hydroreservoirs l2 and 13 respectively, whichfunction as spring members. Similarly, pressure spaces 16 and 17 of thecylinders 14 and are connected with hydroreservoirs 18 and 19.

It will be noted that a line 20 interconnects the pressure spaces 10 and11 and a level control valve 22 is provided for the axle l. The valve 22is provided with ports, A, P, and T and the line 20 is connected to theport A of the valve 22 via line 21. The port P communicates with apressure source and the port T with a tank a Level control valves 22'and 22" are provided for the steering and suspension arrangements 6 and7 respectively and the valves are provided with ports A, A", P, P, and Tand T".

The pressure spaces 16 and 17 are connected by way of lines 23 and 24with the ports A and A" of the valves 22 and 22". The connections P andP lead to pressure sources and ports T and T to tanks.

More specifically, the ports T, T and T" are connected to lines 25, 26and 27 communicating with tanks 25a and 25b. The connections P, P and P"are supplied via a pressure line or conduit 28 from a common source ofpressure denoted generally 29. A pressure limiting valve 30 is providedfor serving as protection against overloads.

The level control valves, 22, 22 and 22" secured on the vehicle body areactuated by means of linkages denoted generally 31, 31' and 31"respectively which are articulated to the rear axle 1 and the steeringarrangements 6 and 7 respectively.

Piston-cylinder units, 32, 32 and 32" are installed in the linkages 31,31 and-3l" and these units are provided with return springs 33, 33' and33". Pistons 34, 34' and 34" for the units 32, 32 and 32" arehydraulically loaded counter to the force of the return springs 33, 33'and 33" by means of a line or conduit 35 which is connected with thepressure line 28 through a pressure control valve 36 equipped with anoutflow aperture. The valve 36 is equipped with a high-pressure port Pe,a consumer connection B and a drain port R.

In the embodiment shown in FIG. 2, components which correspond to thoseillustrated in FIG. I bear the same reference legends and it will beseen that two pressure regulator valves 136" and 136" are provided. Theregulator valve 136' via transmission line effects the piston-cylinderunits 32' and 132' at the left side of the vehicle while the regulatorvalve 136" via transmission line I35" effects the piston-cylinder units32" and 132 at the right side of the vehicle. By virtue of such anarrangement, it is possible to retain a vehicle body in a levelposition, even on a strongly inclined slope in the mountains.

With reference to FIG. 3, pressure regulator valves 236 and 236" areincluded and the valve 236' by way of a transmission line 235 effectsthe two piston-cylinder units 232' and 232" arranged at the rear axle I.The regulator valve 236" effects the piston-cylinder units 32' and 32"for the front wheels 4 and 5 via transmission line 235". Thisarrangement permits the heights of the front and rear sections of thevehicle to be set separately.

The operation of the present invention is as follows:

A certain setting at the pressure control valve 36 means a reduction ofthe pressure in the pressure line 28 which is dependent upon the settingof the pressure limiting valve 30 or the load applied to the settingcylinders respectively to a lower pressure in the system denoted B, andline 35. This pressure acts upon the pistons 34, 34 and 34" of the units32, 32 and 32" and an equilibrium position establishes itself betweenthe forces of the return springs 33, 33' and 33" and the hydraulicpressure force on the pistons 34, 34' and 34". When by adjustment at thepressure control valve 36, the pressure is increased, the springs 33, 33and 33" are compressed more and the length of the units 32, 32' and 32and as a consequence the length of the linkage 31, 31 and 31" increases.The result thereof is a greater ground clearance of the vehicle while onthe other hand such ground clearance is reduced at lower pressure sincethen the lengths of the linkages 31, 31' and 31" are shortened.

By the construction of the pressure control valve with a drain aperture,leakage'losses and other volume variations are compensated for since allvolume variations will bring about a tensioning or relaxing of thereturn springs 33, 33' and 33" and hence an increase or decrease of theset pressure.

Upon a pressure drop in the system denoted B, and 35, the liquid willautomatically flow from port Pe to B until the set pressure is againattained. Upon an increase in pressure, the connection B-R isestablished automatically and since the height of the vehicle dependssolely upon the height of the reduced pressure, it is advisable toprovide, following a proper calibration, a graduation on the controlvalve 36 by which it is possible to directly read the height of thevehicle. Since, due to possible manufacturing tolerances, the length ofthe linkages 31, 31' and 31" may differ from their theoretical lengths,an adjustment to be actuated mechanically may be installed. Similarly,it should be possible to set the initial tensions of the return springs33, 33' and 33".

More particularly, in FIG. 4, a piston-cylinder unit 32 is shown indetail and it will be noted that a piston 34 connected with a piston rod39 moves in a cylinder 38 with the piston being stressed by a spring 33surrounding the rod 39. One end of the spring 33 bears against thepiston 34 while the other end bears against a regulatable component,namely a screw cap or plug 37 through which the piston rod 39 extends.Manifestly, this arrangement enables the initial tension of the spring33 to be set. 1

It will further be seen in H6. 4 that the free end of the piston rod39-is provided with a thread 40 which engages a threaded hole 41 in therod of the linkage 31 and a lock nut 42 is adapted to coact with thethread 40. Obviously, this enables an adjustment of the length of thelinkage 31 to be effected mechanically.

With these possibilities of adfiistment, it is possible to easily bringthe vehicle into the desired starting position for a given or particularload. With the assistance of additional hydraulic shifting means, it isfeasible to connect only the pistoncylinder units of one axle or of onevehicle side with the pressure control valve. The vehicle can be tiltedor canted and such possibility may be of interest, for example, foragricultural equipment or utility vehicles. Of course, alternatively,two separate pressure control valves equipped with cor! responding shiftmeans may be utilized.

The stroke of the piston cylinder units 32, 32' and 32" may be solimited that there still remains spring movement for the cylinders 8, 9,l4 and 15 even in the end positions. Moreover, the stroke may be sogreat that elastic movement is no longer possible due to the fact thesetting cylinders run against their abutment.

Under the invention, it is possible to replace the illustratedhydropneumatic elastic suspension by means of an air suspension or otherelastic suspension. In order to avoid a lowering of the vehicle whenpump 29 is stationary, releasable check valves may be connectedfollowing the level control valves 22, 22' and 22" as is known per se.

What is claimed is: l. A level control assemblage for vehicles forstabilizing the distance between a vehicle body and one or more wheelsupporting means independently of load variations at the vehicle andmaintaining the same constant at a preselectable value, comprisingsetting piston-cylinder units connected in series with spring componentsbetween the vehicle body and the wheel-supporting means, a pressureline, a tank line, linkage means operably related to eachwheel-supporting means, a level control valve incorporated in eachlinkage means adapted to provide communication between the pressure lineor the tank line and the pressure spaces of the piston-cylinder unitsdependent upon the distance between the vehicle body and thewheel-supporting means, piston-cylinder units installed in said linkagemeans whereby the length of the linkage means is continuously variable,each piston-cylinder unit including a single-acting cylinder, a pistonand return spring means for the piston, said piston being hydraulicallyloadable counter to the action of the return spring means, and anadjustable pressure control valve having an outflow aperture formaintaining the pressure in the liquid substantially constant.

2. The level control assemblage for vehicles as claimed in claim 1 inwhich the piston-cylinders of one vehicle side are loaded jointly.

3. The level control assemblage for vehicles as claimed in claim 1including means whereby the heights of the front and rear sections ofthe vehicle can be set separately.

4. The level control assemblage for vehicles as claimed in claim 1including means whereby the basic length of the link- 7 age means isvariable mechanically.

5. The level control assemblage for vehicles as claimed in claim 1including means for adjusting the initial tension of the return springmeans of each piston-cylinder unit installed in the linkage means.

1. A level control assemblage for vehicles for stabilizing the distancebetween a vehicle body and one or more wheel supporting meansindependently of load variations at the vehicle and maintaining the sameconstant at a preselectable value, comprising setting piston-cylinderunits connected in series with spring components between the vehiclebody and the wheelsupporting means, a pressure line, a tank line,linkage means operably related to each wheel-supporting means, a levelcontrol valve incorporated in each linkage means adapted to providecommunication between the pressure line or the tank line and thepressure spaces of the piston-cylinder units dependent upon the distancebetween the vehicle body and the wheel-supporting means, piston-cylinderunits installed in said linkage means whereby the length of the linkagemeans is continuously variable, each piston-cylinder unit including asingle-acting cylinder, a piston and return spring means for the piston,said piston being hydraulically loadable counter to the action of thereturn spring means, and an adjustable pressure control valve having anoutflow aperture for maintaining the pressure in the liquidsubstantially constant.
 2. The level control assemblage for vehicles asclaimed in claim 1 in which the piston-cylinders of one vehicle side areloaded jointly.
 3. The level control assemblage for vehicles as claimedin claim 1 including means whereby the heights of the front and rearsections of the vehicle can be set separately.
 4. The level controlassemblage for vehicles as claimed in claim 1 including means wherebythe basic length of the linkage means is variable mechanically.
 5. Thelevel control assemblage for vehicles as claimed in claim 1 includingmeans for adjusting the initial tension of the return spring means ofeach piston-cylinder unit installed in the linkage means.